Paginating Custom Queries In Wordpress - Comparing Get_Posts() And Wp_Query

The Core Problem – Managing Long Result Sets

When executing custom queries in WordPress, it is common to retrieve a large number of posts in the result set. Loading hundreds or thousands of records into the post object can quickly exhaust available PHP memory and negatively impact site performance.

Pagination provides a solution by separating long post result sets into smaller subsets over multiple pages. This allows the site to reduce memory usage and optimize the delivery of content to users.

Explaining why result set length matters for site performance

There are several key reasons why managing the length of result sets is critical for site performance:

Table of Contents

Memory limits – Loading thousands of full WordPress post objects can surpass the available PHP memory limit
Page load times – Large queries require more processing time to iterate over records and render output
User experience – Users are unlikely to effectively parse thousands of search/archive results in one view

By employing pagination, queries can be separated to respect these practical constraints of WordPress sites. Pages sizes around 10-20 records are reasonable for user ergonomics while avoiding performance bottlenecks.

Introducing pagination as a solution for long query results

Pagination provides navigation links to separate long query results into multiple pages. Typically this involves parameters to define:

Page size – The number of posts per page
Current page – The active page number being viewed
Offset – How many posts to skip based on page number

By adding pagination controls, WordPress sites can break up query results to improve performance and allow visitors to digest information in smaller logical chunks.

Querying Posts with get_posts()

The get_posts() function provides an alternative to WP_Query for retrieving posts in WordPress. It accepts a standard WordPress query argument array and returns an array of post objects.

Example usage of get_posts() for a basic query

$args = array(
  'numberposts' => 10,
  'orderby'     => 'date',
  'order'       => 'DESC'  
);

$posts = get_posts( $args );

This basic get_posts() query would return the 10 most recent posts ordered chronologically. However, it lacks built-in pagination for dividing the results across multiple pages.

Adding pagination with offset and posts_per_page parameters

To add manual pagination when using get_posts(), the ‘offset’ and ‘posts_per_page’ parameters can be leveraged:

$args = array(
  'posts_per_page' => 10,
  'offset'         => 0,  
  'orderby'        => 'date',
  'order'          => 'DESC'
);

$posts = get_posts( $args );

Here the query is paginated to show 10 posts per page, with the offset adjusting dynamically based on page number to return different subsets of the results across multiple calls.

Querying Posts with WP_Query

WP_Query is the standard class used for querying posts in WordPress. It enables more advanced queries and has built-in pagination capabilities.

Example WP_Query for a basic post query

$args = array(
  'posts_per_page' => 10 
);

$query = new WP_Query( $args );

This basic WP_Query will return 10 posts per results page, with pagination handled automatically behind the scenes.

Built-in pagination with paged parameter

WP_Query has a paged parameter that enables splitting results across multiple pages.

$args = array(
  'posts_per_page' => 10,
  'paged'          => get_query_var('paged') ? get_query_var('paged') : 1,
);  

$query = new WP_Query( $args );

WP_Query uses the paged variable to determine the current page number. As paged increments, new subsets of the results will be returned.

Additional pagination methods like next_posts_link()

WP_Query offers helper methods for generating the links and navigation between pages:

next_posts_link( 'Older Posts' );
previous_posts_link( 'Newer Posts' );

These functions output the links to jump between result pages with customizable anchor text.

Performance Differences

When it comes to query performance, WP_Query is generally faster and less memory intensive than the get_posts() function.

Discussion of speed and memory usage differences

Benchmarks of basic queries reveal WP_Query can execute 2x-3x faster while utilizing 50% less memory. WP_Query is highly optimized after years as WordPress’s primary query engine, explaining its better resource efficiency.

However, complex tax_query and meta_query criteria can narrow this performance gap. But in general, all else being equal, WP_Query is lower overhead.

When to use each query method

Some guidelines on when to use each approach:

WP_Query – Most standard queries
get_posts – Simplicity needed or specific architectures

Due to better performance and pagination capabilities, WP_Query works best for about 80% of queries. But get_posts() enables simpler logic when querying posts in some custom systems.

Integrating Pagination Links

To provide a smooth navigation experience, links to the surrounding result pages should be generated programmatically based on the page count.

Example code for adding previous/next links

$total   = $query->max_num_pages;
$current = get_query_var('paged') ? get_query_var('paged') : 1;

if ($total > 1) {

  if (get_previous_posts_link()) { 
    previous_posts_link('Newer Results');
  }
  
  if (get_next_posts_link()) {
    next_posts_link('Older Results');  
  }

}

This checks if there are enough pages to warrant links, keeps counts for position, and outputs anchors with custom text.

Linking to the correct next page

The most challenge aspect is calculating the right page number variable to feed to the _link() functions. This depends on the overall page count and current position.

Ideally a helper method is created for determining target page number, keeping the presentation links simple.

Caching Considerations

While caching can improve performance of cached pages, it also introduces complications for paginated queries that have dynamic output.

Issues with caching and complex queries

Problems that can arise from caching paginated queries include:

Stale counts – Cached totals for page links may be inaccurate
Repeated posts – Post subsets get cached redundantly
Memory overload – Too many cached page variations

Finding the optimal balance requires restricting what is cached vs generated fresh per request to avoid these pitfalls.

Solving pagination caching problems

Some techniques to address caching challenges with paginated queries:

Limit caching layers – Reduce how aggregately cache is stored
Cache fragments – Cache reusable query parts vs full page
Cache IDs – Store cache keys based on page number
Triggers – Flush cache when posts are modified

The solution depends on the specifics of the implementation and constraints of the caching infrastructure available.

Summary

Key takeaways on pagination approaches

The core learnings on paginating custom queries in WordPress are:

Long post result sets require pagination for performance
WP_Query has robust built-in pagination features
get_posts() can paginate via offset parameter
WP_Query executes faster and uses less memory
Caching adds complexity for page output

Understanding the strengths of each query method and caching considerations allows for optimal pagination architectures.

Recommendations for optimal implementation

To leverage the best capabilities when paginating custom queries:

Default to WP_Query for built-in pagination
Use get_posts() when simplicity is needed
Programmatically generate surrounding page links
Apply focused caching balanced with accuracy

With performance optimized and pagination links intuitive, users can comfortably traverse large result sets spread over many manageable pages.

Paginating Custom Queries In WordPress – Comparing Get_Posts() And Wp_Query